1. Field of the Invention
The patent document relates to the field of radio communication technology, and particularly, to a device-to-device (D2D) discovery method, an eNodeB and a user equipment.
2. Description of Related Art
With the development of radio multimedia services, people's demand for a high data rate and user experience is increasing, thereby putting forward a higher requirement for system capacity and coverage of a traditional cellular network. On the other hand, the popularity of applications such as a social network, short-distance data sharing and local advertisement and so on makes people's demand for knowing nearby persons or things which they are interested in and communicate with (Proximity Services) increase gradually. The traditional cellular network with the eNodeB as a data transmission node center has apparent limitations in the aspect of supporting the high data rate and proximity services, and in this demand background, the Device-to-Device (D2D) technology representing a new direction for future communication technology development emerges at the right moment. With the application of the D2D technology, the load of the cellular network can be relieved, which reduces the battery consumption of the user equipment, increases the data rate, and improves the robustness of the network infrastructure, thereby meeting the above demand for high data rate services and proximity services well.
With the D2D technology, it can work at an authorized frequency band or a non-authorized frequency band, and allow multiple user equipments supporting a D2D function (i.e. D2D User Equipments (D2D UEs)) to perform direct discovery/direct communication with network infrastructure or without network infrastructure. There are mainly three application scenarios of the D2D.
1) A UE1 and a UE2 performs data interaction under coverage of the cellular network, and data of the user plane do not go through the network infrastructure, as a mode 1 in FIG. 1;
2) It is UE relay transmission in area with weak coverage/without coverage, as a mode 2 in FIG. 1, a UE4 with worse signal quality is allowed to communicate with the network via a nearby UE3 with network coverage, which can help the operator expand the coverage and enhance the capacity;
3) In a case that an earthquake or emergency situation occurs and the cellular network cannot work normally, direct communication between devices is allowed, as a mode 3 in FIG. 1, both a control plane and a user plane between a UE5, a UE6 and a UE7 perform single-hop or multi-hop data communication without the network infrastructure.
The D2D technology generally includes the D2D discovery technology and the D2D communication technology.
The D2D discovery technology refers to the technology used for judging/determining that two or more D2D user equipments are mutually adjacent (for example, within a range that direct D2D communication can be performed) or used for judging/determining that the first user equipment is adjacent to the second user equipment. Generally, the opposite side can be discovered by sending or receiving discovery signals/information between the D2D user equipments, and under the coverage of the cellular network, the network can assist the D2D user equipments to perform D2D discovery;
the D2D communication technology refers to the technology that part or all of communication data between the D2D user equipments can be directly communicated without the network infrastructure.
When the D2D discovery is performed between the user equipments, it is usually required to send a discovery signal between the user equipments to perform detection, when the opposite side can receive the signal, it indicates that the two user equipments are adjacent, and then discovery between the two user equipments is completed through information interaction with the eNodeB or direct information interaction between the user equipments. At present, in the D2D discovery in a scenario with network coverage, ways of the user equipments acquiring discovery signal resources through competition or an eNB uniformly allocating discovery signal resources to the user equipments are generally adopted, and states of the user equipments and locations of the user equipments in the cell are not considered in all these methods, which easily causes a low signal resource utilization rate and a conflict between signal resources.